As a fish jumps vertically out of the water, assume that only two significant forces act on it: an upward force F exerted by the tail fin and the downward force due to gravity. A record Chinook salmon has a length of 1.50 m and a mass of 53.5 kg. If this fish is moving upward at 3.00 m/s as its head first breaks the surface and has an upward speed of 6.30 m/s after two-thirds of its length has left the surface, assume constant acceleration and determine the following.
a) the salmon's acceleration (m/s^2 upward)
b) the magnitude of the force F during this interval

Question

As a fish jumps vertically out of the water, assume that only two significant forces act on it: an upward force F exerted by the tail fin and the downward force due to gravity. A record Chinook salmon has a length of 1.50 m and a mass of 53.5 kg. If this fish is moving upward at 3.00 m/s as its head first breaks the surface and has an upward speed of 6.30 m/s after two-thirds of its length has left the surface, assume constant acceleration and determine the following. 
a) the salmon's acceleration (m/s^2 upward)
b) the magnitude of the force F during this interval

anonymous · Answer

First, we need to determine the change in distance. That is, the difference in the length of the fish that is above the water. We then need the change in velocity. We can then use the equation:
$$V_f^2 = V_i^2 + 2*a*d$$
to find a.

Then use$$F=ma$$to find the force.

anonymous · Answer

Small correction: you don't need the difference in the velocities. Just the difference in the length of the fish.